Gases are used for various purposes in industrial, medical, and food and beverage applications. Such uses include medical oxygen for life support, medical nitrous oxide for anesthesia, medical helium for Magnetic Resonance Imaging equipment, medical nitrogen for cryosurgery, nitrogen for food packaging, carbon dioxide for beverage carbonation, industrial nitrogen for purging welding oxygen, welding argon, carbon dioxide for laser cutting and nitrogen use by the silicon chip industry. Many of these applications, including medical and food and beverage uses, directly implicate health and safety.
Gas is delivered to a location at which it is needed by a distribution system that includes devices to regulate or distribute gas and pipe or tubing connecting the devices in the distribution system. Commonly, gas is supplied to a distribution system from tanks or cylinders that have fittings that are connected to the distribution system. Gas cylinders, pipes, valves, and other components of a gas distribution system are connected to each other by connection fittings. Because of safety considerations, the United States Food and Drug Administration and Compressed Gas Association have recommended that all medical and industrial gas cylinders have the valve connection fittings that are retained such that only authorized persons can remove and reinstall them.
Currently, connection fittings used to connect distribution systems to gas cylinders can be removed and replaced with a wrench while the cylinder is full. Because a fitting can be removed before a scheduled replacement of an empty cylinder by appropriately trained and knowledgeable persons, it is possible that a fitting may be removed and an incorrect connection made. For example, there have been some cases of Nitrogen tanks being delivered to medical applications where Oxygen cylinders should have been delivered. Unauthorized persons removed a Nitrogen connection fitting from a Nitrogen cylinder and replaced it with an Oxygen connection fitting. This allowed Nitrogen to flow into an Oxygen system used to ventilate patients. Breathing the Nitrogen gas asphyxiated several people. There is now a requirement that medical gas cylinders have the fittings attached such that they cannot easily be removed.
Known methods for preventing removal of fittings from gas cylinders include brazing a fitting to a valve, drilling and pinning a fitting to a valve, and use of a lock wire. The various methods of retaining a fitting to a valve or other component have disadvantages.
A lock wire will not prevent removal of a connection fitting. Removal of a lock wire and the connection to which it was attached will not damage the fitting or connected device and therefore allows installation of a wrong fitting. Removal of a lock wire will leave evidence of the removal. However, a lock wire does not prevent harm caused by incorrect connections in a gas distribution system.
Brazing a fitting onto the a valve will prevent the fitting from being removed by unauthorized persons. However, if the fitting is damaged (a common event), the cylinder must be sent to a special facility for the valve to be replaced. This is expensive for three reasons. First the cylinder is out of service and cannot be rented or sold. Second, removal of the valve and fitting are expensive operations requiring highly skilled labor to weld and braze the fitting. Third, a replacement valve and fitting must be installed.
Drilling and pinning a connection fitting into a valve will also prevent the fitting from being removed by unauthorized persons. However, as with brazing a fitting, the cost to replace a damaged fitting is very high. Further, the integrity of the valve is jeopardized by the hole that is drilled to accept the pin.
The brazing and pinning methods retain a connection fitting such that the fitting is not easily removed and if removal is accomplished, the connection no longer is usable. Installation of brazed or pinned fittings is labor intensive and requires special tooling, removal of the cylinder from service, disassembly of the valve and purchase of a repair kit to replace non-reusable valve components.
Accordingly, a need remains for a method of preventing unauthorized removal of connection fittings from valves and other components of gas distribution systems that does not damage the fitting or component. A need also exists for a method of preventing unauthorized removal of connection fittings from components of gas distribution systems that allows quick installation and removal of the fitting for authorized service of the gas distribution system.